X9ballX said:
what would happen if i put something thats 12 gauge and smaller inside?
What do you mean? A 12-gauge shotgun will run 12-gauge ammo. It will not run 20-gauge or anything else.
As well as gauge, there are different shell lengths. 2 3/4" is and always has been the standard length, and then you have 3" shells (magnums) and 3.5" shells (super magnums). There's not much of a practical
need for 3" or 3.5" shells unless you goose hunt, but if you want the flexibility to be able to use them in the future, simply buy a gun that will accept those shell lengths.
So to reiterate, you have
gauge, which is equivalent to "caliber" in a rifle, and then you have shell length. All modern shotguns will run 2 3/4" shells as they are standard length; a shotgun marked for 3" will feed both 2 3/4" and 3" shells, and a shotgun marked for 3.5" will feed 2 3/4", 3" and 3.5" shells.
As far as getting yourself into an OBAMA'S GON' TAKE MAH GUNS AWAY frenzy, don't fall into that trap - especially with shotguns. Nothing you're going to buy for $400 will be covered by a ban. Sporting shotguns are not in any danger, hence why they're still available and cheap.
As others have said, you really need to slow down,
read, and have some sit-down conversations with your friends who know firearms. Forget about buying, for now; you need to have a basic knowledge of firearms first, and respectfully, it's obvious that you have no clue right now...